Category: New York

Bus Stop Spacing and Network Legibility

I had an interesting interview of the annoying kind, that is, one where my source says something that ends up challenging me to the point of requiring me to rethink how I conceive of transportation networks. On the surface, the interview reaffirmed my priors: my source, a mobility-limited New Yorker, prefers public transit to cars and is fine with walking 500 meters to a bus stop. But one thing my source said made me have to think a lot more carefully about transit network legibility. At hand was the question of where buses should stop. Ages ago, Jarrett suggested that all other things equal (which they never are), the best stop spacing pattern is as follows:

The bus stops on the north-side arterials are offset in order to slightly improve coverage. The reason Jarrett cites this doesn’t occur much in practice is that there would also be east-west arterials. But maybe there aren’t a lot of east-west arterials, or maybe the route spacing is such that there are big gaps between major intersections in which there’s choice about which streets to serve. What to do then? My source complained specifically about unintuitive decisions about which streets get a bus stop, forcing longer walks.

In the case of the most important streets, it’s easy enough to declare that they should get stops. In Brooklyn, this means subway stations (whenever possible), intersecting bus routes, and important throughfares like Eastern Parkway or Flatbush. Right now the B44 Select Bus Service on Nostrand misses Eastern Parkway (and thus the connection to the 3 train) and the M15 SBS on First and Second Avenues misses 72nd Street (and thus the southernmost connection to Second Avenue Subway). However, there is a bigger question at hand, regarding network legibility.

Bus networks are large. Brooklyn’s current bus network is 550 km, and even my and Eric Goldwyn’s plan only shrinks it to about 340, still hefty enough that nobody can be expected to memorize it. Passengers will need to know where they can get on a stop. For the sake of network legibility, it’s useful to serve consistent locations whenever possible.

This is equally true of sufficiently large subway networks. Manhattan subway riders know that the north-south subway lines all have stops in the vicinity of 50th Street, even though the street itself isn’t especially important, unlike 42nd or 34th. In retrospect, it would have been better to have every line actually stop at 50th, and not at 49th or 51st, but the similarity is still better than if some line (say) stopped at 47th and 54th on its way between 42nd and 59th. A bad Manhattan example would be the stop spacing on the 6 on the Upper East Side, serving 68th and 77th Streets but not the better-known (and more important) 72nd and 79th.

There are similar examples of parallel subway lines, some stopping on consistent streets, and some not. There are some smaller North American examples, i.e. Toronto and Chicago, but by far the largest subway network in the world in a gridded city is that of Beijing. There, subway stops near city center are forced by transfer locations (Beijing currently has only one missed connection, though several more are planned), but in between transfers, they tend to stop on consistent streets when those streets are continuous on the grid.

But outside huge cities (or cities with especially strong grids like Chicago, Philadelphia, and Toronto), consistent streets are mostly a desirable feature for buses, not subways. Bus networks are larger and less radial, so legibility is more important there than on subways. Buses also have shorter stop spacing than subways, so people can’t just memorize the locations of some neighborhood centers with subway stops (“Nation,” “Porte de Vincennes,” etc.).

In the other direction, in cities without strong grids, streets are usually not very long, and the few streets that are long (e.g. Massachusetts Avenue in Boston) tend to be so important that every transit route intersecting them should have a stop. However, streets that are of moderate length, enough to intersect several bus lines, are common even in interrupted grids like Brooklyn’s or ungridded cities like Paris (but in London they’re rarer). Here is the Paris bus map: look at the one-way pair in the center on Rue Reaumur and Boulevard Saint-Denis (and look at how the northbound bus on Boulevard de Strasbourg doesn’t stop at Saint-Denis, missing a Metro transfer). There are a number of streets that could form consistent stops, helping make the Parisian bus network more legible than it currently is.

As with all other aspects of legibility, the main benefits accrue to occasional users and to regular riders who unfamiliar with one particular line or region. For these riders, knowing how to look for a bus stop (or subway station, in a handful of large cities) is paramount; it enables more spontaneous trips, without requiring constantly consulting maps. These occasional spontaneous trips, in turn, are likelier to happen outside the usual hours, making them especially profitable for the transit agency, since they reduce rather than raise the peak-to-base ratio. (Bus operating costs mostly scale with service-hours, but very peaky buses tend to require a lot of deadheading because they almost never begin or end their trip at a bus depot.)

The main takeaway from this is that bus network redesigns should aim to stop buses on parallel routes at consistent streets whenever possible, subject to other constraints including regular stop spacing, serving commercial nodes, and providing connections to the rail network. To the extent cities build multiple parallel subway lines, it’s useful to ensure they serve stations on consistent streets as well when there’s a coherent grid; this may prove useful if New York ever builds a subway under Utica and extends the Nostrand Avenue Line, both of which extensions were on the drawing board as recently as the 1970s.

Radial Metro Networks for Portions of Cities

I’ve harped about the necessity of radial metro networks, looking much like the following schematic:

However, in practice such pure radial networks are rare. Some networks have parallel lines (such as Paris and Beijing), nearly all have lines intersecting without a transfer at least once (the largest that doesn’t is Mexico City), some have chordal lines and not just radial or circular lines, and nearly all have lines that meet twice. Often these variations from pure radii are the result of poor planning or a street network that makes a pure radial system infeasible, but there are specific situations in which it’s reasonable for lines to meet multiple times (or sometimes even be parallel). These come from the need to built an optimal network not just for the whole city but also notable portions of it.

The unsegmented city

The diagram depicted above is a city with a single center and no obvious sub-areas with large internal travel demand. If the city is on a river, it’s not obvious from the subway map where the river passes, and it’s unlikely its non-CBD bank has a strong identity like that of the Left Bank of Paris, South London, or Brooklyn and Queens.

Among the largest metro networks in the world, the one most akin to the diagram above is Moscow. It has seven radial lines through city center (numbered 1-10, omitting the one-sided 4, the circular 5, and the yet-incomplete 8). They have some missed connections between them (3/6, 3/7, 6/9), and one pair of near-parallel lines (2/10, meeting only at Line 10’s southern terminus), but no parallel lines, and no case in which two lines cross twice. And Moscow’s development is indeed oriented toward connecting outlying areas with city center. Connections between areas outside the center are supposed to use the circular lines (5 and 14, with 11 under construction).

In a relatively monocentric city, this is fine. Even if this city is on the river, which Moscow is, it doesn’t matter too much if two neighborhoods are on the same side of the river when planning the network. Even in polycentric cities, this is fine if the sub-centers get connections via circular lines or the odd chordal line (as will eventually happen when Los Angeles builds a real subway network with such chords as Vermont and Sepulveda).

The segmented city

London and Paris are both segmented by their rivers, and their wrong sides (South London, Left Bank) both have strong regional identities, as does to some extent East London. New York, partitioned into boroughs by much wider waterways than the Thames and Seine, has even stronger sub-identities, especially in Brooklyn. I do not know of a single New Yorker whose commute to work or school involves crossing a bridge over a river on foot, nor of any case of anyone crossing a bridge in New York on foot (or bike) except for recreational purposes; in Paris I do so habitually when visiting the Latin Quarter, and at a conference in 2010 another attendee biked from Porte de Vincennes to Jussieu every day.

With a difficult water boundary, the wrong-side part of the city became a center in its own right. Downtown Brooklyn and the Latin Quarter should both be viewed as sub-centers that failed to become CBDs. The Latin Quarter, the oldest part of Paris outside the Ile de la Cite, declined in favor of the more commercial Right Bank as the city grew in the High and Late Middle Ages; Downtown Brooklyn declined in favor of more concentration in Manhattan and more dispersion to other centers (often in Queens) over the course of the 20th century.

Early 20th century New York and Paris were not polycentric cities. There was no everywhere-to-everywhere demand. There was demand specifically for travel within Brooklyn and within the Left Bank. To this day, the connections to the Latin Quarter from Right Bank neighborhoods not on Line 4 are not great, and from Nation specifically the alternatives are a three-seat ride and a long interchange at Chatelet. Ultimately, this situation occurs when you have a region with a strong identity and strong demand for internal travel larger than a neighborhood (which can be served by a few subway stops on a single line) but smaller than an entire city.

In this case, a radial subway network (which neither the New York City Subway nor the Paris Metro is) could justifiably have multiple crossings between two lines, ensuring that lines provide a coherent network for internal travel. South London is a partial example of this principle: not counting the Wimbledon branch of the District line, the South London Underground network is internally connected, and the best route between any two South London stations stays within South London. In particular, the Victoria and Northern lines cross twice, once at Stockwell and once at Euston, in a city that has a generally radial metro system.

Don’t go overboard

The need to serve internal travel within portions of a city is real, and it’s worthwhile to plan metro networks accordingly. But at the same time, it’s easy to go overboard and plan lines that serve only travel within such portions. Most of the examples I give of weak chordal lines – the G train in New York, Line 10 and the RER C in Paris, Line 6 in Shanghai – serve internal demand to the wrong side of a city divided by a river; only Shanghai’s Line 3 is an exception to this pattern, as a weak chordal line that doesn’t come from city segmentation.

In the cases of the G and M10, the problem is partly that the lines have compromises weakening them as radials. The G has too many missed connections to radial lines, including the J/Z and the entire Atlantic-Pacific complex; M10 terminates at Austerlitz instead of extending east to the library, which is the second busiest Left Bank Metro stop (after Montparnasse) and which has a particularly strong connection to the universities in the Latin Quarter.

But Line 6 is constrained because it doesn’t serve Lujiazui, just Century Avenue, and the RER C does serve the library but has exceptionally poor connections to the CBD and other Right Bank destinations. It’s important to ensure the network is coherent enough to serve internal demand to a large segment of the city but also to serve travel demand to the rest of the city well.

Good transfers

Serving the entire city hinges on good transfers. The most important destination remains city center, so lines that aren’t circumferential should still aim to serve the center in nearly all cases. Internal demand should be served with strategic transfers, which may involve two lines crossing multiple times, once in or near city center and once on the wrong side of the river.

The main drawback of multiple crossings is that they are less efficient than a pure radial network with a single city center crossing between each pair of lines, provided the only distinguished part of the city is the center. Once internal travel to a geographic or demographic segment is taken into account, there are good reasons to slightly reduce the efficiency of the CBD-bound network if it drastically raises the efficiency of the secondary center-bound network. While demographic trends may come and go (will Flushing still be an unassimilated Chinese neighborhood in 50 years?), geographic constraints do not, and place identities like “Left Bank” and “Brooklyn” remain stable.

Note the qualifiers: since the CBD remains more important than any secondary center, it’s only acceptable to reduce CBD-bound efficiency if the gain in secondary center-bound efficiency is disproportionate. This is why I propose making sure there are good transfers within the particular portion of the city, even at the cost of making the radial network less perfect: this would still avoid missed connections, a far worse problem than having too many transfer points.

So what?

In New York, London, and Paris, the best that can be done is small tweaks. However, there exist smaller or less developed cities that can reshape their transit networks, and since cities tend to form on rivers and bays, segmentation is common. Boston has at least two distinguished wrong-side segments: East Boston (including Chelsea and Revere) and Greater Cambridge. East Boston can naturally funnel transit through Maverick, but in Greater Cambridge there will soon be two separate subway spines, the Red and Green Lines, and it would be worthwhile to drag a rail connection between them. This is why I support investing in rail on the Grand Junction, turning it into a low-radius circular regional rail line together with the North-South Rail Link: it would efficiently connect the Green Line Extension with Kendall.

More examples of segmented cities include the Bay Area (where the wrong-side segment is the East Bay), Istanbul (where Europe and Asia have separate metro networks, connected only by Marmaray), Stockholm (where Södermalm and Söderort are separated by a wide channel from the rest of the city, and Kungsholmen is also somewhat distinguished), and Washington (where the wrong side is Virginia). In all of these there are various compromises on metro network planning coming from the city segmentation. Stockholm’s solution – making both the Red and Green Lines serve Slussen – is by far the best, and the Bay Area could almost do the same if BART were connected slightly differently around Downtown Oakland. But in all cases, there are compromises.

The Formula for Frequent Transit Networks

As I’m working on refining a concrete map for Brooklyn buses, I’m implementing the following formula:

Daily service hours * average speed per hour = daily frequencies * network length

In this post I’m going to go over what this formula really means and where it is relevant.

Operating costs

The left-hand side represents costs. The operating costs of buses are proportional to time, not distance. A few independent American industry sources state that about 75-80% of the cost of bus service is the driver’s wage; these include Jarrett Walker as well as a look at the payrolls in Chicago. The remaining costs are fuel, which in a congested city tracks time more than distance (because if buses run slow it’s because of stop-and-go traffic and idling at stops or red lights), and maintenance, which tracks a combination of time and distance because acceleration and braking cycles stress the engine.

This means that the number of service hours is fixed as part of the budget. My understanding is that the number in Brooklyn is 10,000 per weekday. I have seen five different sources about bus speeds and service provision in New York (or Brooklyn) and each disagrees with the others; the range of hours is between 9,500 and 12,500 depending on source, and the range of average speeds is between 9.7 km/h (imputed from the NTD and TransitCenter’s API) and 11 km/h (taken from schedules). The speed and hours figures are not inversely correlated, so some sources believe there are more service-km than others.

On a rail network, the same formula applies but the left-hand side should directly include service-kilometers, since rail operating costs (such as maintenance and energy) are much more distance- than time-dependent; only the driver’s wage is time-dependent, and the driver’s wage is a small share of the variable costs of rail operations.

Creating more service

Note that on a bus network, the implication of the formula is that higher speed is equivalent to more service-hours. My current belief, based on the higher numbers taken from schedules, is that 14 km/h is a realistic average speed for a reformed bus network: it’s somewhat lower than the average scheduled speed of the B44 SBS and somewhat higher than that of the B46 SBS, and overall the network should have somewhat denser stop spacing than SBS but also higher-quality bus lanes canceling out with it. The problem is that it’s not clear that SBS actually averages 14 km/h; my other sources for these two routes are in the 12-13 km/h range, and I don’t yet know what is correct. This is on top of the fact that faster transit attracts more paying riders.

Another way to create more service is to reduce deadheading and turnaround times. This is difficult. Bus depots are not sited based on optimal service. They are land-intensive and polluting and end up in the geographic and socioeconomic fringes of the city. The largest bus depot in New York (named after TWU founder Mike Quill) is in Hudson Yards, but predates the redevelopment of the area. In Brooklyn the largest depots appear to be East New York (more or less the poorest neighborhood in the city) and Jackie Gleason (sandwiched between a subway railyard and a cemetery). Figuring out how to route the buses in a way that lets them begin or end near a depot so as to reduce deadheading is not an easy task, but can squeeze more revenue-hours out of an operating cost formula that is really about total hours including turnaround time and non-revenue moves.

Service provision

The right-hand side of the equation describes how much service is provided. The network length is just the combined length of all routes. Daily frequency is measured in the average number of trips per day, which is not an easily understandable metric, so it’s better to convert it to actual frequencies:

Frequency Daily trips
15 minutes 6 am-9 pm, 30 minutes otherwise 5-1 am 70
15 minutes 24/7 96
5 minutes 7-9 am, 5-7 pm, 10 minutes otherwise 6 am-10 pm, 30 minutes 10 pm-12 am 124
5 minutes 7-9 am, 5-7 pm, 7.5 minutes otherwise 6 am-10 pm, 15 minutes 10 pm-12 am, 30 minutes overnight 164
6 minutes 6 am-10 pm, 10 minutes otherwise 5-12 am, 30 minutes overnight 188
5 minutes 6 am-10 pm, 10 minutes otherwise 5-12 am, 20 minutes overnight 228
3 minutes 7-9 am, 5-7 pm, 5 minutes otherwise 6 am-10 pm, 10 minutes otherwise 5-12 am, 20 minutes overnight 260

Daily trips are given per direction; for trips in both directions, multiply by 2. There are internal tradeoffs to each number of daily trips between peak and off-peak frequency and between midday frequency and span. But for the most part the tradeoff is between the average number of daily trips per route and the total route-length. This is the quantitative version of Jarrett’s frequency-coverage tradeoff. In reality it’s somewhat more complicated – for example, average speeds are lower at the peak than off-peak and lower in the CBD than outside the CBD, so in practice adding more crosstown routes with high off-peak frequency costs less than providing the same number of revenue-km on peaky CBD-bound buses.

It’s also important to understand that this calculation only really works for frequent transit, defined to be such that the ratio of the turnaround time to the frequency and length of each route is small. On low-frequency routes, or routes that are so short that their total length is a small multiple of the headway, the analysis must be discrete rather than continuous, aiming to get the one-way trip time plus turnaround time (including schedule padding) to be an even multiple of the headway, to avoid wasting time. On regional rail, which often has trains coming every half hour on outer tails and which is much more precisely scheduled than a street bus ever could be, it’s better to instead get the length of every route from the pulse point to the outer end to be an integer or half-integer multiple of the clockface headway minus the turnaround time.

Where is New York?

All of my numbers for New York so far should be viewed as true up to a fudge factor of 10-15% in each direction, as  my source datasets disagree. But right now, Brooklyn has about 10,500 revenue-hours per weekday (slightly more on a school day, slightly fewer on a non-school day) and an average speed of about 10.5 km/h, for a total of 110,000 revenue-km. Its bus network is 550 km long, counting local and limited versions of the same bus route as a single route but counting two bus routes that interline (such as the B67 and B69) separately; interlining is uncommon in Brooklyn, and removing it only shortens the network by a few km. This means that the average bus gets 200 runs per day, or 100 per direction.

Based on the above table, 100 runs per direction implies a frequency somewhat worse than every 5 minutes peak and every 10 off-peak. This indeed appears to be the case – nearly half of Brooklyn’s network by length has off-peak weekday frequency between 10 and 15 minutes, and the median is 12. At the peak, the median frequency, again by route-length, is 7 minutes. 7 minutes peak, 12 off-peak with some extra evening and night service works out to just less than 100 runs a day in each direction.

This exercise demonstrates the need to both shrink the network via rationalization to reduce the number of route-km and increase speed to raise the left-hand side of the equation. SBS treatments increased the speed on the B44 and B46 by 30-40% relative to the locals (not the limiteds), but just keeping the network as is would onl permit 130-140 buses per weekday per direction, which is more frequency but not a lot of frequency. The 7.5-minute standard that appears to be used in Toronto and Vancouver requires more; Barcelona’s range of 3-8 minutes implies an average of 5-6 and requires even more.

Where could New York be?

It’s definitely possible to get the number of daily frequencies on the average Brooklyn bus route to more than 200 in each direction. In Manhattan this appears true as well (the big question is whether the avenues can get two-way service), and in the Bronx 250 is easy. But even 200 in Brooklyn (which implies perhaps 350 km of network) requires some nontrivial choices about which routes get buses and which don’t, cutting some buses that are too close to other routes or to the subway. I’m not committing to anything yet because the margin calls happen entirely within the 10-15% fudge factor in my datasets.

The main reason I post this now is that I believe the formula is of general interest. In any city that wants to rationalize its transit system (bus or rail), the formula is a useful construction for the tradeoffs involved in transit provision. You can look at the formula and understand why some systems choose to branch: at the same average frequency the busiest parts of the network would get more service. You can also understand why some systems choose not to branch: at some ranges of frequency, the outer ends would get so little frequency that it would discourage ridership.

What is high frequency?

I’m using 5-6 minutes as a placeholder value beyond which there’s no point in raising frequency if there’s no capacity crunch. This isn’t quite true – on a 15-minute bus trip, going from 6 minutes between buses to 3 is a 14% cut in worst-case trip time including wait – but at this point higher frequency is at best a second-order factor. It’s not like now, when going from 15 minutes to 6 would reduce the worst-case trip time on the same bus trip by 30%.

The actual values depend on trip length. An intercontinental flight every hour is frequent; a regional train every hour is infrequent; a city bus every hour might as well not exist. One fortunate consequence is that bus trips tend to be shorter in precisely the cities that can most afford to run intensive service: dense cities with large rail networks for the buses to feed. New York’s average NYCT bus trip (excluding express buses) is 3.5 km; Chicago’s is 4.1 km; Los Angeles’s is 6.7 km. Los Angeles can’t afford to run 6-minute service on its grid routes, but trips are long enough that 10-minute service may be good enough to start attracting riders who are not too poor to own a car.

How YIMBY Reflects New York’s Priorities

The conversation about YIMBY and zoning seems to be centered around San Francisco. Googling YIMBY Guardian gives me two articles about Northern California out of the top three results (the third is an op-ed about London). But the real origin of YIMBY is New York. The term started with New York YIMBY, which was always a real estate magazine rather than an activist movement. San Francisco YIMBY adopted it and intended to publish under the umbrella of New York YIMBY before eventually going its own way, buoyed by SF YIMBY founder Sonja Trauss’s strong political organizing skills, which are much better than those of the New York YIMBY founder. However, for the most part the goals and actions of YIMBY are still based on New York-centric assumptions, which may not apply elsewhere.

This does not mean that YIMBY is a New York imposition. On the contrary. But some of the specific details come from New York’s context. They port more easily to Paris, Tokyo, and London than to San Francisco, Boston, and other American cities.

Commercial versus residential upzoning

I’ve argued for commercialization before. Near-CBD residential neighborhoods are prime locations for high-end retail and office uses, leading to expansion or even migration of the CBD. Midtown historically arose this way, beginning with commercialization around Fifth Avenue, and so did the Paris CBD, which is well to the west of the historic core; in London the primary CBD is still the City, but the West End has many jobs as well.

However, in practice, New York needs residential development more than commercial development. There is demand for new office space, particularly from the tech industry, but this is a minority of the city’s employment. In contrast, residential rents are very high, and there is very little construction permitted; according to data from the Department of Housing and Urban Development, the average over the last few years has been about 2.5 annual units permitted per 1,000 residents (in Tokyo the average is 10.7). As a result, New York’s activist YIMBY group, called Open New York, focuses on residential and mixed projects and not on purely commercial ones.

When a city does not allow the construction of office space in or near its center, jobs are displaced to sprawling suburbs. This is routine all over the US, where high-rise CBDs are surrounded immediately by residential neighborhoods with little political will for commercialization, and thus people work either in the CBD or in auto-centric suburban office parks. San Francisco is especially prone to this trend, since the origin of the tech industry is not in the city but in the office parks stretching from Redwood City to San Jose. If Uber, Airbnb, Slack, and Twitter don’t have room to grow in SoMa they will move to a suburb hungry for sales tax revenues. Nonetheless, SF YIMBY has opposed the plan to add office space to SoMa on the grounds that residential space is of prime importance.

The politics of rent stabilization

New York has rent control (which means the real rent is fixed) on a small number of apartments, all continuously occupied since 1971, mostly in rich Manhattan neighborhoods. It has wider rent stabilization in a large (though not overwhelming) fraction of rental units, which permits some real rent increases, determined politically every year but averaging about 1%. This status quo has many problems, chief of which is that the details of rent stabilization incentivize harassing tenants into leaving or looking for tenants who’d only stay for a short period of time. However, the status quo is politically stable.

The importance of this is that YIMBYs in New York don’t have to take a position on rent stabilization, or on related issues like inclusionary zoning (moreover, New York’s high real estate profits ensure that inclusionary zoning, which is a tax on revenue, has less impact than in cheaper cities like Portland, where the same tax on revenue represents a much higher tax on profits). SF YIMBY adopts this approach, but this comes into tension with California’s politics in which populists demand more rent control, even applying it to new buildings.

YIMBYs can’t honestly support rent control on new buildings and expect the private sector to keep providing housing. In New York it’s irrelevant because nobody calls for such policy, but San Francisco has a more active leftier-than-thou community (as does Paris, but this is expressed in museum exhibits about Che Guevara and not in rent control on new buildings).

The frontier of the Millennial middle class

When the middle class moves into a low-income area it’s called gentrification. However, the same trend can be observed in areas that are already well-off, including the neighborhood I grew up in, Tel Aviv’s Old North. The Old North was never poor: it was built in the 1930s and early 40s and the initial population was middle-class German immigrants fleeing Hitler. Nonetheless, by the 1980s the area was unfashionable, and the retail on the main commercial drag, Dizengoff Street, declined in favor of newer shopping malls. But since the late 1990s, younger people have moved in, making the area more in vogue, often renovating old buildings from the 1930s (which are a UNESCO heritage site, even though locally they’re viewed as dinghy). The demographic entering the neighborhood is the same as the one that gentrifies poorer neighborhoods (such as Florentin), so it’s worthwhile to view this as part of the same trend.

I bring this up because in New York this trend of a middle-class frontier includes a wide swath of neighborhoods, some poor and gentrifying (Harlem, Washington Heights, Bushwick, Lower East Side) but others already comfortable (Astoria, Upper West Side, Morningside Heights, South Brooklyn). Open New York has a policy of focusing on supporting construction in areas that are already rich and gentrified, to avoid the risk of gentrification in places like Washington Heights. As a strategy, it makes sense for New York, as well as for other city whose frontier of young middle-class urban transplants is mostly in well-off areas, like Chicago, Boston, and Paris. It’s weaker in San Francisco specifically, since there the frontier is largely the Mission, where gentrification is unavoidable.

The role of the suburbs

New York may be permitting only 2.5 housing units per 1,000 residents every year, but its in-state suburbs build even less. Westchester’s average between 2011 and 2017 is 0.9, Nassau County’s is 0.7, and Suffolk County’s is 0.8. Moreover, the dynamic of suburban white flight is well-understood around the region, and criticizing suburban-style exclusionary zoning is easy from within the city. There is animosity between the city and the suburbs, a feature shared with many areas in the American Rust Belt, and this makes it easier to demand more building in the city. (In the other direction, it’s easier to demand more construction in the city if there are no city-suburb social tensions at all.)

In the American Sunbelt, the situation is different. There is less city-suburb animosity – often the boundaries of the city include de facto suburban areas while excluding dense areas. (This is to some extent true of New York but the examples are all on the New Jersey side, which New Yorkers ignore.) Just saying “we need more housing” doesn’t sound progressive. What’s more, even in places like Houston and Austin, the city proper votes liberal and wants internal political movements to align on the left, let alone in California; in these areas, upzoning sounds like a bad deregulation.

Counterexample: single-family zoning

In exactly one respect, YIMBY groups in North America have proposed something that departs from the movement’s New York origins: they call for replacing single-family zoning with what they call missing middle, such as townhouses with two to four apartments per building. Missing middle is in turn relevant mostly to Canada, where there are mid- and high-rise neighborhoods and single-family neighborhoods and not much in between. In the US, everything is missing except single-family and CBD high-rises.

In New York, of course, there is no missing middle – for one, there are rowhouses, which would count as missing middle elsewhere. But more to the point, these rowhouses and townhouses are on the outer margins of the subway’s coverage area (such as Southern Brooklyn) or even beyond it (such as Kew Gardens Hills), and aren’t where there is the most demand. The demand is for converting surviving low-rise buildings in inner neighborhoods to mid- and high-rise apartment buildings, so this is what Open New York and urbanists in general focus on.

Which cities are like New York when it comes to YIMBY?

New York’s situation is the same as in the European cities I’m familiar with. Missing middle density in Paris happens on the outer branches of the RER network, whereas the real demand is for more housing in the city and a handful of rich inner suburbs in Hauts-de-Seine, and the same is true in Stockholm, London, Zurich, and other expensive European cities, even though they’re less dense than Paris so they might have rowhouses (like London) or missing middle density that needs to be replaced with mid-rise (like Zurich).

The politics in New York, where it’s easier to sidestep concerns about gentrification by just focusing on upzoning rich areas, is also similar to that of cities that never experienced white flight. This includes nearly all major cities in the developed world outside the US; the biggest exception I know of is Brussels, where the politics is complicated by the fact that middle-class residents are often affiliated with the EU and many only stay temporarily.

Commercialization of near-CBD areas is also more common in Europe, so there is less need to argue about that specifically. Zoning is also looser in the sense of permitting small offices, such as those of doctors, lawyers, and accountants, in residential zones. Thus the focus is exclusively housing, especially in the largest cities, i.e. London and Paris, where traffic congestion is such that there is less risk of job sprawl than in (say) Stockholm.

Finally, London and Paris have no rent control. Both have political controversies around this – Paris passed rent control but it was stricken down by the courts on administrative grounds, and in London some people are calling for rent control – but the current status quo is market-rate. The European cities I’m familiar with that have rent control do not have vacancy decontrol, unlike in the US, but instead have long waitlists, measured in years and in some extreme Stockholm examples even decades, so YIMBYs can more readily point to long waitlists as evidence that more housing construction is needed.

New York’s specific social issues are much more American than European, but the way they interact with its urban layout and transportation network is unique, partly because it has decent public transit unlike anywhere else in North America and partly because it’s just bigger. This interaction in turn makes its housing politics look somewhat more European as far as YIMBY is concerned. This suggests that people interested in making housing affordable should be especially excited to implement the proposed program in big global first-world cities outside New York, led by London and Paris (and Tokyo, which is already sufficiently YIMBY).

Here and in London, the need for more housing is dire, as in New York. What’s more, it’s not possible to just propose missing middle density in single-family areas or even mid-rises like California’s SB 827 and say something about great cities, because Paris is already great. (In London this is easier – there are rowhouses in zone 2 of the Underground.) There are some unusually short buildings here and there, down to 3-4 floors, but usually replacements have to be much bigger, so they’d be perhaps 12-15 floors. And in the most desirable neighborhoods, around the 8th and 16th, full high-rises are warranted. The one point of light is that such a program is unlikely to run into California’s gentrification concerns, if only because the main target areas for upzoning are the richest city neighborhoods in France.

Bus Branching

There are two standard reasons why public transit should limit branching. The first is that it reduces frequency on the branches; this is Jarrett Walker’s reason, and distantly the reason why New York doesn’t interline more than two subway services anywhere except 60th Street Tunnel. The second is that it makes schedules more fragile, first because services have to be scheduled more precisely to alternate among branches, and second because delays on one branch propagate to the others. And yet, rail and bus networks still employ branching, due to benefits including better coverage and focusing frequency where demand is the highest. This is especially common on regional rail, where all services are scheduled and often interact with the mainline network, so the second problem of branching is present no matter what. Metro systems instead have less branching, often because they only serve dense areas so that the main benefits of branching are absent. But what about buses?

I posit that bus branching is more valuable in low-density areas than in high-density areas. If an area only has demand for a bus every 30 minutes, and some farther-out places only have demand for an hourly bus, then it’s fine to branch the route in two. The bus would only be useful with some timed transfers at the inner end – maybe it’s feeding a regional train station with a train every half hour – but the Zurich suburbs have half-hourly clockface schedules with timed bus/rail connections and maintain high mode share for how low their density is.

In the other direction, look at Manhattan specifically. I’ve been looking at its bus network even though I’m only supposed to redesign Brooklyn’s. I’ve mentioned before that my epistemology is that if the presence of factor A makes solution B better, then the absence of factor A should make solution B worse. I noticed that the Brooklyn bus network has very little branching: the only route numbers that branch are the B41 and B38, and the only routes with different numbers that share the majority of their lengths are the B67 and B69 (which reverse-branch). However, Manhattan has extensive branching: the M1/2/3/4 share the Madison and Fifth Avenue one-way pair, and the M101/102/103 share the Third and Lexington one-way pair. Understanding why would be useful even if I only care about Brooklyn: if there is a good reason for Manhattan buses to branch then I should consider adding branching in Brooklyn where appropriate, and even if it’s inappropriate, it’s useful to understand what special circumstances make branching good in Manhattan but not in Brooklyn.

As it is, I don’t believe the branching in Manhattan is useful for Brooklyn. This comes from several reasons, at least one of which implies it’s not really useful for Manhattan either, and by extension for other high-density regions.

Base frequency

You can run a bus that comes every half hour on a schedule, making it possible to interline two hourly routes evenly. With some discipline you can go down to 15 minutes, or possibly even 10: Vancouver runs 12-minute limited buses on 4th Avenue on a clockface schedule with on-board fare collection and shared lanes, but there is signal priority at nearly all intersections and relatively little car traffic since the West Side’s street network is rich in arterial roads and distributes cars across other routes (i.e. Broadway, 12th, and 16th Avenues).

In contrast, it’s not really feasible to run buses on a schedule when they come every 5 minutes. There can be a printed schedule, but buses won’t follow it reliably. Once frequency hits about once every 3 minutes, regular street buses bunch so much that adding more buses doesn’t increase passenger capacity, but even in the 5-10 minute range, schedules are less important than headway management, unless the bus has extensive BRT treatments reducing schedule variance. This means that if a bus comes every 10 minutes and is scheduled on headway management, then branching the route means each branch gets service every 20 minutes scheduled on headway management as well. Few passengers would want to ride such a route. This is the worst region for branching, the 7.5-15 minute range in which branches force passengers to use buses that are both infrequent and irregular.

The highest-frequency routes can branch with less risk. If a 5-minute bus branches in two, then each branch gets 10-minute service, at which point reliable schedules are still desirable but not absolutely necessary. How much service do the Manhattan bus trunks run? In the following scheme, peak means the busiest hour in the morning in the peak direction, and off-peak means the lowest frequency between the morning and afternoon peaks, which is usually around 11 am.

M1: 13 buses per hour peak (8 limited, 5 local), 5 off-peak (all local)
M2: 9 peak, 4 off-peak
M3: 6 peak, 6 off-peak
M4: 12 peak (5 limited, 7 local), 6 off-peak (all local)

M101: 6 peak, 6 off-peak (8 in the busiest off-peak hour, 2-3 pm)
M102: 5 peak, 4 off-peak
M103: 5 peak, 4 off-peak

What we see is that Manhattan branches precisely in the worst frequency range. The buses are frequent enough that it’s not possible to run them on a timetable without either much better segregation from traffic than is feasible (even waving away politics) or massive schedule padding, but they still require passengers in Upper Manhattan to wait 10-15 minutes for their specific branch. One might expect that Bus Time would make it easier on passengers by telling them where the bus is, but no, ridership has actually fallen since apps were introduced (and this fall predates the entry of app-hailed TNCs into the city). It turns out passengers like being able to rely on easily memorable clockface schedules, or else on frequencies so high that they only need to wait 5 minutes, not 15.

The street network

Even one-time visitors to New York notice that the avenues in Manhattan are all one-way. This features prominently in the Manhattan bus network, which employs consistent one-way pairs on First/Second, Third/Lex, Madison/Fifth, and Ninth/Tenth. Moreover, again as every visitor to New York knows, Central Park occupies a large blob of land in the middle, interrupting Sixth and Seventh Avenues.

The upshot is that there are more north-south routes north of 110th Street than south of it. This is roughly the branch point on the three trunks that branch (First/Second only carries the M15). In Harlem, there’s demand for buses on Lenox (i.e. Sixth) and Seventh, both of which are two-way there. There’s also commerce on an interpolating route, Manhattan/St. Nicholas, which is effectively 8.5th Avenue in most of Harlem. Farther west, Ninth/Columbus is no longer a useful through-route north of 110th, but instead Tenth/Amsterdam is two-way, and one of the two buses using the Columbus/Amsterdam one-way pair on the Upper West Side, the M11, indeed goes two-way on Amsterdam north of 110th.

This situation occurs very frequently in cities without gridded street networks. One trunk route will split in two, heading to different former villages that were incorporated into the city as it industrialized and grew. Manhattan is unusual among gridded cities in that its avenues are one-way, forcing buses into one-way pairs south of Harlem that, together with Central Park, ensure there are more useful routes north of 110th than south of it. But among cities without a planned street network this is typical.

As a check, let’s look at the bus networks in two ungridded American cities: Boston and Providence. Do they have a lot of interlining, involving one trunk route splitting in two farther out? Yes, they do!

Here is Providence. Going west of Downcity, there are two major routes to Olneyville, Westminster and Broadway, but beyond Olneyville there are four main streets, so each of the two inner corridors carries two bus routes, and one of these four routes even splits in two farther out. Going north, Charles Street carries four routes, branching off at various locations. Going east there’s a bus tunnel to College Hill carrying many routes, but even outside the tunnel, the one-way pair on Angell and Waterman carries three buses, which split in East Providence. And going south and southwest, Broad Street carries multiple routes, and one of its branches, Elmwood, carries two, splitting farther south.

Here is Boston. Unlike in Providence, buses don’t converge on city center, but on subway stations, so the map is much less clean. However, we see the same pattern of trunk routes splitting into branches. For example, going south of Ruggles, many routes go southeast to Dudley and then south on Warren Street, splitting to various destinations in Dorchester, Mattapan, and Hyde Park on the way. Going southwest of Forest Hills we see many routes use Washington Street, some staying on it and branching in Dedham and some veering west to West Roxbury and branching there. Elsewhere in the system we see the same pattern going north of Maverick and Oak Grove, northeast of Malden, west of Harvard (briefly on Mount Auburn), and northwest of Alewife.

One-seat rides and reverse-branching

I have repeatedly criticized the practice of reverse-branching on subway networks, especially New York, in which two train routes share tracks in an outlying area (such as Queens Boulevard) and then split heading into the center (such as Eighth Avenue on the E versus Sixth Avenue on the F). I did so on the same grounds that any branching is suspect: it reduces frequency on specific routes, and makes the schedule more fragile as delays propagate to more of the network. Moreover, the issue of schedule fragility gets worse if many routes share tracks at some point during their journey, whereas with conventional branching there are only two or three branches per trunk and the trunks form self-contained systems. Finally, reverse-branching lacks the main benefit of conventional branching, as it does not concentrate traffic in the core, where there’s most demand.

These issues are present on bus networks, with two modifications:

  1. The value of one-seat rides is somewhat higher. Transferring between buses is less nice than transferring between subways: in a Dutch study about location decisions, people’s disutility of out-of-vehicle time on buses was 1.5 times as high as on trains.
  2. Buses can overtake each other and, even without overtakes, run much closer together than trains. The limiting factor to capacity on buses is schedule fragility and bunching and not stopping distances. This means that reverse-branching is less likely to lead to cascading delays – buses do not have a 2-minute exclusion zone behind them in which no buses may enter.

This means that reverse-branching is more defensible on buses than on trains. However, even then, I don’t think it’s a good idea. At least in Manhattan, reverse-branching consists of avenues in Upper Manhattan that have buses going to both the East Side and the West Side: the M7 (serving the Ninth/Tenth pair) and the M102 both run on Lenox, and the M4 and M104 (running on Broadway to Midtown) both run on Broadway in Morningside Heights. These splits both reduce the frequency available to bus riders and should be eliminated. East-west service should be provided with high-quality bus routes on the main streets, especially 125th (which needs a full subway) but also 116th, 135th, 145th, and 155th.

The snag is that grids don’t work well unless they are complete. The Manhattan grid isn’t complete through Upper Manhattan, because 116th and 135th are discontinuous, without a direct connection from Central Harlem to Morningside Heights and West Harlem. However, the M7 route duplicates the 2 and 3 trains, so it’s not necessary for east-west connectivity. The M4 route doesn’t duplicate the subway, but does duplicate the M101, which runs on 125th Street and Amsterdam (and isn’t a reverse-branch because the M11 terminates shortly after 125th), so it’s not useful by itself.

Should buses branch?

There is one solid reason for buses to branch: if the street network has more major routes closer to the center than in outlying areas, then buses running on the outer arterials should come together close to the core. This is common enough on cities with haphazard street networks. It may also be reinforced if there are weak circumferential streets (Sydney is one such example). In contrast, cities with gridded street plans, even broken grids like those of Brooklyn and Tel Aviv, should have little to no bus branching.

If a bus does branch, it should ideally be extremely frequent on the trunk, so that even the branches have decent headway-based service. I’m not willing to commit to a maximum headway, but Barcelona and Toronto both have at worst 8-minute headways on their bus grids, so if that is indeed the maximum then a bus shouldn’t branch if its off-peak frequency is worse than every 4 minutes and better than every 10-20 (the more reliable the timetable is, the lower the upper limit is, since it’s possible to run on a timetable at higher frequency). In my case of interest, Brooklyn, there is exactly one bus route that comes at least every 4 minutes off-peak: the B46 on Utica runs 16 buses per hour in each direction, counting both local and limited (SBS) routes.

The area in which buses absolutely should not branch – strong interconnected networks of arterials (not necessarily grids – Paris’s network counts too), running buses every 5-15 minutes off-peak – is exactly where most strong bus networks are. It’s rare to have a bus that has extremely high frequency all day, because in most functional city such a bus would be a subway already; as it is, Utica has long been New York’s second priority for subway service, after Second Avenue. So for the most part, the places where buses are the strongest are precisely those where branching is the most deleterious. Low-frequency networks, perhaps connecting to a suburban train station with a timed transfer, should add bus branching to their planning toolkit, but high-frequency urban networks should not.

Gentrifier Stereotypes

The American discourse about gentrification is full of stereotypes that the participants don’t recognize as such. For example, a widely-shared Buzzfeed article created an entire theory out of a single busybody who was responsible for half of the police complaints on their West Harlem block. The main check on stereotypes – “that’s racist” – only works when the stereotypes resemble the forms of racism society is most familiar with. The history of white racism against black people in the US is so different that it colors what Americans perceive as racial stereotypes and what they don’t. So as public service, I’d like to give some examples to draw commonalities between stereotypes in other cities I’ve lived in (Tel Aviv, Vancouver, Paris) and familiar anti-gentrification rhetoric.

Tel Aviv

Last decade, there was an influx of black refugees into working-class areas of South Tel Aviv, centered on Levinsky Park. The area is underpriced relative to its job access, courtesy of Central Bus Station, a failed urban renewal project that attracted crime; already in the 1990s it was nicknamed Central Stench (tsaḥana merkazit; Central Station is taḥana merkazit) and lampooned in a popular comic as a literal gateway to hell. The neighborhood’s response was violent, and the discourse within Israel is divided into people who wish the refugees imprisoned and deported from the country and people who wish them forcibly dispersed around the country.

Other parts of South Tel Aviv have been gentrifying since the 1990s, centered on Florentin. South Tel Aviv’s right-wing Jewish working class began connecting the two trends. A few years ago I saw a widely-shared Facebook post claiming that the influx of black refugees is deliberately engineered by developers as a ploy to gentrify the neighborhood. The theory, as I recall, is that black people are so odious that developers are using them to engineer white flight, after which they’ll evict the refugees, demolish the neighborhood’s mid-rise housing stock, and erect luxury towers.

Vancouver

In the last decade or so Vancouver has seen rising rents and even faster-rising housing prices, and the region’s white population is blaming Chinese people. In 2016, British Columbia passed a 15% tax on residential buyers who are not Canadian citizens or permanent residents; the tax was phrased neutrally, but the target was predominantly Chinese, and 21% of correspondence from citizens to the government on the issue was explicitly Sinophobic. In a city with rapid immigration, it should not be a surprise that new buyers tend to be immigrants, often on work or investor visas, but the region has a moral panic about Chinese people buying condos and houses as investments and leaving them empty.

The specific stereotypes of Chinese people in Vancouver vary. When I lived in Vancouver I encountered some light generic stereotyping (“people in Richmond are aggressive drivers”), but nothing connoting poverty, even though Richmond is poorer than Surrey, which some people I met compared with Camden, New Jersey. The language I see in the media concerning housing goes the other way: Chinese immigrants are stereotyped as oligarchs laundering ill-begotten wealth.

Paris

Like people in every other highly-toured region, Parisians hate the tourists. Seeing small declines in city population over the 2009-14 period, city electeds decided to blame Airbnb, and not, say, low housing construction rates (raising rents), a falling birth rate, or commercialization in city center. The mayor of the 1st arrondissement, Jean-Francois Legaret, called Airbnb “a true catastrophe for Central Paris.” The 1st arrondissement has high residential incomes; the lower-income parts of the city are the 10th, 11th, 13th, 18th, 19th, and 20th.

Rich and poor stereotypes

An ethnic or national group can stereotype another group as rich, poor, or both. White stereotypes of black people in the US and Europe are, within each ethnic group, associated with poverty: crime, aggressive physicality, laziness, indifference to education, proclivity for certain kinds of music and sport. Anti-Semitism today invokes stereotypes of the rich: greed, political subversion, disloyalty to the nation, corruption, success with money. Islamophobic stereotypes tend toward stereotypes of poverty, but are sometimes also bundled with stereotypes of Gulf money. In the last few decades Sinophobic stereotypes transitioned from ones of poverty (treating the Chinese as a faceless horde) to ones of wealth, similar to anti-Semitic stereotypes, to the point that people in Vancouver forget Richmond’s low incomes and people in New York forget the high poverty rates of Asian-New Yorkers and the overcrowding in Chinatown.

But as in the case of South Tel Aviv, the stereotypes can merge. The racists in South Tel Aviv blend two groups they hate – middle-class leftists and poor non-Jews – into one mass, blaming them for a trend that is usually blamed on the rich and the middle class. Historically, anti-Semitism was fully blended: the Jew was simultaneously poor and rich, wretched and exploitative, communist and capitalist, overly studious and overly physical. This blending of stereotypes was overt in Nazi propaganda, but also in the softer anti-Semitism directed against immigrants to the US.

The urban as a foreigner

Nationalists and populists stereotype cities like prewar anti-Semites stereotype Jews. The urban poor are lazy criminals, the rural poor are honest workers; the urban rich are exploitative capitalists sucking life out of the country, the rural rich are successful small business leaders; the urban middle class are bo-bo globalists, the rural middle class is the very definition of normality. This mentality is hard to miss in anti-urbanist writers like Joel Kotkin, and more recently in articles trying to portray an opposition between the Real Country (in the US but also in Israel and France) and the Urban Elites.

The definition of what is rural and what is urban is fractal. In the South, Long Island is part of New York; on Long Island, Long Island is Real America, distinct from the city that Long Island’s residents fled in the 1950s and 60s. Within cities the Real Country vs. Urban Elite opposition can involve the outer city vs. the inner city, as in Toronto, where Rob Ford won the mayoral election by appealing to outer-urban resentment of David Miller’s attempt to redistribute street space from cars to public transit. But it is in many cases demographic rather than geographic: the newcomer is the new rootless cosmopolitan.

In this mentality, the newcomer can be a rich gentrifier displacing honest salt-of-the-earth third-generation residents by paying higher rents or a refugee doing the same through living multiple people to a bedroom (or even both, in the case of some San Francisco programmers). In either case, the newcomer is a foreigner who doesn’t belong to the city’s culture and does not deserve the same access to city resources. People who build housing for this foreigner are inherently suspect, as are businesses that cater to the foreigner’s tastes. The demands – removal of access to housing – are the same regardless of whether the foreigners so stereotyped are poor or rich, and the stereotypes of wealth and poverty mix easily. That anti-gentrification activism looks so similar regardless of which social class it targets suggests that ultimately, any argument made is an excuse justifying not liking outsiders very much.

Reverse-Branching Does not Save You the Transfer

I wrote a detailed proposal about why New York should deinterline, and how. I got a lot of supportive comments (in the transit blogging sense, i.e. nitpicking), but also some pushback, arguing that people like their one-seat rides, and making them transfer under a more coherent system would make their riding experience worse. I could go on about how London is facing the same problem and is choosing to invest a lot of money into deinterlining in order to increase train capacity, but in the case of New York, there’s a blunter answer: what one-seat ride? The extent of reverse-branching on the subway does not really give people one-seat rides, and New York City Transit is making service decisions that do not maximize one-seat rides even when doing so would be relatively painless.

Outer branches

Most outer branches with just one route naturally offer direct service to the route’s trunk line. Let’s look at the current subway_map, and compare it with my proposed deinterlining, which is again this:

Today, riders on the West End Line only have service on the D, so they only have a one-seat ride to Sixth Avenue. Riders on the Sea Beach Line only have the N, and riders on the local Brighton Line trains only have the Q, so they only have one-seat rides to the Broadway express trains, and if they want to travel to Prince Street or 8th Street-NYU on the R they have to change trains at Canal, which is not a cross-platform transfer. Only a handful of stations get genuine choice between the two trunk lines: 36th Street on the D and N, and the inner few express stops on the B and Q, say up to Newkirk Avenue. These are express stops, with more ridership than the locals, but they’re not the majority of ridership on the subway in Southern Brooklyn. The majority of riders have to deal with the drawbacks of both reverse-branching (slow, infrequent trains) and coherent service (fewer one-seat rides).

Queens Boulevard has the same situation: local and express patterns mix up in a way that makes the choice of one-seat rides much weaker than it appears on the map. Riders at the local stations can choose between the M and the R, two trains that are never more than a few blocks apart in Midtown; only one station on either line is inconvenient to access from the other, 57th Street/7th Avenue, the least busy stop on the Broadway Line in Midtown on a passengers per platform basis (49th and 5th have less ridership but have two platform tracks and no Q service). The express stops get more serious choice, between the E and F, but those are just three stations: Jackson Heights-Roosevelt Avenue, Forest Hills-71st Avenue, and Kew Gardens-Union Turnpike. Queens Plaza has E, M, and R service, but passengers actually getting on at Queens Plaza can equally get on at Queensboro Plaza and ride the N, W, or 7.

Genuine choice between two relatively widely-separated trunk lines on the same trunk only exists in two and a half places in New York: the Central Park West Line offers a choice between the B and C trains, the Nostrand Avenue Line offers a choice between the 2 and 5 trains, and the inner half of the White Plains Line offers a choice between the 2 and 5 trains off-peak (at the peak the 5 runs express, so local stations only get the 2).

Cross-platform transfers

New York is blessed with cross-platform interchanges, usually between local and express trains on the same line. Riders on the 1 train are used to transferring to the 2 and 3 trains cross-platform at 96th Street; in the morning, the 1 train’s busiest point is actually from 103th Street to 96th, and not heading into Midtown. With 170,000 boardings at its stations north of 96th per weekday, the 1 is much busier than Nostrand (with 60,000 weekday boardings) or the combined total of local Central Park West stations from 72nd to 116th (with 65,000 boardings). It’s also slightly busier than the White Plains Road Line, let alone the inner segment with both 2 and 5 service (which has 95,000 boardings).

In Queens, a similar situation occurs on the 7. The stations east of Queensboro Plaza, excluding 74th Street-Broadway (where the transfer to the Queens Boulevard Line is), have a total of 215,000 weekday boardings. The trains fill at the outer end and then discharge at 74th Street as most passengers transfer, not cross-platform, to the faster Queens Boulevard Line; then they fill again at the stations to the west and discharge at Queensboro Plaza, which has a cross-platform transfer to the N and W.

This is relevant to some of the few segments of the subway where reverse-branching offers choice between different trunk lines. Passengers on the Nostrand Avenue Line could transfer cross-platform at Franklin Avenue, where the platforms aren’t much narrower than at 96th Street and Broadway, where passenger volumes are almost three times as high. Similarly, passengers on the Central Park West Line and its branches to Washington Heights and Grand Concourse could transfer cross-platform at 125th Street or at Columbus Circle; Columbus Circle is extremely busy already with origin-and-destination traffic, and the interchanges between local and express passengers could not possibly overwhelm it.

Only one place has a difficult connection: 149th Street-Grand Concourse, the interchange between the 2, 4, and 5 trains. This also happens to be the most difficult deinterlining project in general, because of the merger of the 2 and 3 further south; it requires either closing the northernmost two stations on the 3, or opening up a few blocks of Lenox Avenue to construct a pocket track. Because of the disruption involved, this project can be left for last, and come equipped with more passageways at 149th Street, just as London is first deinterlining the Northern line to the south (raising peak capacity on the Bank branch from 26 trains per hour to 32) and leaving the north for later (which would raise capacity further to 36 tph).

NYCT has deinterlined in the past

Upper Manhattan witnessed two deinterlinings in the second half of the 20th century, one in the 1950s and another in the 1990s. The service NYCT inherited from its three predecessor networks had systematic route nomenclature taking into account conventional and reverse branching.

On the IRT, West Side trains were numbered 1 (to Van Cortlandt Park), 2 (to the White Plains Road Line), and 3 (to Harlem-148th Street), and Lexington trains were numbered 4 (to the Jerome Avenue Line), 5 (to the White Plains Road Line), and 6 (to the Pelham Line); 2, 4, and 5 trains ran express, 3 and 6 trains ran local, and 1 trains could be either local or express. In the 1950s, NYCT changed this system on the West Side so that all 1 trains became local and all 3 trains became express. This was the result of track layout: the junction at 96th Street is flat if 3 trains have to cross over to the local tracks and 1 trains have to cross over to the express tracks, but under today’s present service pattern there are no at-grade conflicts. NYCT chose capacity and reliability over offering one-seat rides from West Harlem and Washington Heights to the express tracks.

On the IND, trains were identified by letters. A, C, and E trains ran on Eighth Avenue and B, D, and F trains on Sixth Avenue; A and B trains went to Washington Heights, C and D trains to Grand Concourse, and E and F trains to the Queens Boulevard Line. Local and express trains were identified using letter doubling: a single letter denoted an express train, a doubled one (e.g. AA) a local. The single vs. double letter system ended up discontinued as few trains consistently run express (just the A and D) and several run a combination of local and express (the B, E, F, N, and Q), and NYCT slowly consolidated the trains on Eighth and Sixth Avenue until there were only seven services between them. Eventually the B and C switched northern terminals, so that now the C runs as the local version of the A and the B as something like the local version of the D. Passengers in Washington Heights who wish to use Sixth Avenue Line have to transfer.

The situation on the IND wasn’t as clean as the deinterlining on the IRT. But it shows two important things. First, changes in train service have made the original reverse-branching less tenable from an operational perspective. And second, the value of a one-seat ride from Washington Heights or Central Harlem to local tracks is limited, since everyone takes the express train and transfers at Columbus Circle.

How Deinterlining Can Improve New York City Transit

New York is unique among the major subways of the world in the extent of interlining its network has. All routes share tracks with other routes for part of the way, except the 1, 6, 7, and L. The advantage of this system is that it permits more one-seat rides. But the disadvantages are numerous, starting with the fact that delays on one line can propagate to nearly the entire system, and the fragile timetables lead to slower trains and lower capacity. New NYCT chief Andy Byford just released a plan calling for investment in capacity, called Fast Forward, focusing on accessibility and improved signaling, but also mentioning reducing interlining as a possibility to increase throughput.

I covered the interlining issue more generally in my article about reverse branching, but now I want to explain exactly what it means, having learned more about this issue in London as well as about the specifics of how it applies to New York. In short, New York needs to reduce the extent of reverse branching as much as possible to increase train speed and capacity, and can expect serious gains in maximum throughput if it does so. It should ultimately have a subway map looking something like this:

Lessons from London

In London, there is extensive interlining on the Underground, but less so than in New York. The subsurface lines form a complex interconnected system, which also shares tracks with one branch of the Piccadilly line, but the Northern, Central, Victoria, Jubilee, and Waterloo and City lines form closed systems (and the Bakerloo line shares tracks with one Overground line). The Northern line reverse-branches: it has two central trunks, one through Bank and one through Charing Cross; one southern segment, with through-trains to both trunks; and two northern branches, each sending half its trains to each trunk. The other closed systems have just one trunk each, and as a result are easier to schedule and have higher capacity.

As the Underground moves to install the same high-capacity signaling on more and more lines, we can see what the outer limit of throughput is on each system. The Northern line’s new moving-block signaling permits 26 trains per hour on the Bank trunk and 22 on the Charing Cross trunk. When the Battersea extension opens, reverse branching on the south will end, pairing the older line to Morden with Bank and the new extension with Charing Cross, and capacity will rise to 32 tph per trunk. Planned improvements to transfer capacity at Camden Town, the northern branch point, will enable TfL to permanently pair each northern branch with one central trunk, raising capacity to 36 tph per trunk. Moreover, TfL expects moving block signaling to raise District line capacity from 24 tph to 32, keeping the current reverse branching. The Victoria line already runs 36 tph and the Jubilee line soon will too, while the Central line runs 35 tph. So 36 vs. 32 seems like the difference coming from the final elimination of reverse branching, while more extensive reverse branching reduces capacity further.

The reason complex branching reduces capacity is that, as delays propagate, the schedule needs to incorporate a greater margin of error to recover from unexpected incidents. It also slows down the trains, since the trains are frequently held at merge points. The general rule is that anything that increases precision increases capacity (such as automation and moving block signaling) and anything that reduces precision reduces capacity; reverse branching reduces timetable precision, because each train can be delayed by incidents on more than one line, making delays more common.

What deinterlining in New York entails

NYCT has its work cut out for it when it comes to deinterlining. There are eight different points in the system where reverse-branching occurs – that is, where lines that do not share track in Manhattan (or on the G trunk outside Manhattan) share tracks elsewhere.

  1. The 2 and 5 trains share tracks on the Nostrand Avenue Line.
  2. The 2 and 5 also share tracks in the Bronx.
  3. The A and C trains share tracks on the two-track narrows through Lower Manhattan and Downtown Brooklyn.
  4. The A and D share the express tracks on Central Park West while the B and C share the local tracks.
  5. The E and F share the express tracks on Queens Boulevard, while the M and R share the local tracks, the E and M share the tunnel from Queens to Manhattan, and the N, R, and W share a different tunnel from Queens to Manhattan.
  6. The B and Q share tracks in Brooklyn, as do the D and N.
  7. The F and G share tracks in South Brooklyn.
  8. The M shares the Williamsburg Bridge tracks with the J/Z but runs in Manhattan on the same tracks as the F.

NYCT should work to eliminate all of the above reverse branches. The easiest to start with is #6: the junction at DeKalb Avenue should be set to keep the B and D trains together and to keep the N and Q together rather than to mix them so that the B shifts to the Q tracks and the D to the N tracks. This requires no changes in physical infrastructure, and has especially high benefits as the junction delays trains by several minutes in each direction. Moreover, the loss of one-seat rides is minimal: the BDFM and NQRW run closely parallel in Manhattan and intersect with a transfer at Herald Square in addition to the inconveniently long BQ/DNR transfer at Atlantic Avenue.

Another relatively easy reverse branch to eliminate is #8, a recent introduction from the 2010 service cuts. Previously, today’s M route in Queens and Manhattan was covered by the V train, which turned on the Lower East Side, while the M ran the same route as the J/Z, merging onto the R and thence the N in Brooklyn at rush hour. Today’s route is thus an M-V merger, which railfans including myself hoped would help decongest the L by creating an alternative route from Williamsburg to Midtown. Unfortunately, such decongestion has not happened, perhaps because gentrification in Williamsburg clusters near the L and not near the J or M.

Harsh decisions

Fixing the reverse-branching at DeKalb Avenue and on the Williamsburg Bridge is painless. The other reverse branches require a combination of hard decisions and new infrastructure.

Fixing reverse branches #3 and #4 requires no capital investment, just political will. Reverse branch #4 is there because there’s demand for two routes’ worth of capacity in the tunnel from Brooklyn but there’s only one express line on Eighth Avenue, and that in turn is the result of reverse branch #3; thus these two issues should be tackled together.

NYCT should decide between having the A and C trains run express between 145th and 59th Streets and the B and D trains run local, or the other way around. This is not an easy decision: either Washington Heights or Grand Concourse would get consigned to local trains. North of 145th the total number of boardings is 102,000 at B/D stations compared with 79,000 on the A/C, but conversely Concourse riders can change to the express 4 trains whereas Washington Heights’ only alternative is the local 1. However the A and C run, express or local, the E should run the opposite in Manhattan – it can merge to either the local or express tracks – and the express trains should continue to Brooklyn. The map I made doesn’t distinguish local from express service, but my suspicion is that Washington Heights should get express trains, on account of its long commutes and lack of fast alternatives.

The same problem of harshness occurs in reverse-branch #5. In theory, it’s an easy fix: there are three track pairs in Queens (Astoria, Queens Boulevard local, Queens Boulevard express) feeding three tunnels to Manhattan (63rd, 60th, and 53rd Streets). In practice, the three Manhattan trunks have astonishingly poor transfers between them in Midtown. Nonetheless, if it does nothing else, NYCT should remove the R from Queens Boulevard and route all 60th Street Tunnel trains to Astoria; together with fixing DeKalb Avenue, this would separate the lettered lines into two closed systems, inherited from the BMT and IND.

However, undoing the connection between the BMT and the IND probably requires constructing a transfer station in Long Island City between Queensboro Plaza and Queens Plaza, which involves a few hundred meters of underground walkway. Even then, the connection cannot possibly be convenient. The saving grace is that Eighth Avenue, Sixth Avenue, and Broadway are close enough to one another that passengers can walk to most destinations from any line.

Subsequently, NYCT should make a decision about whether to send express Queens Boulevard trains to 63rd Street and Sixth Avenue and local trains to 53rd and Eighth, as depicted in the above map, or the other way around. The problem is that the merge point between 53rd and 63rd Street Tunnels is one station east of Queens Plaza, at a local station, and thus the true transfer point is Roosevelt Avenue, far to the east. Riders on the local stations west of Roosevelt would get no choice where to go (though they get little choice today – both the E and M serve 53rd Street, not 63rd). The argument to do things as I depict them is to give the local stations access to 53rd Street; the argument to switch the lines is that there is more demand on 53rd than 63rd and also more demand on the express tracks than the local tracks, so the busiest lines should be paired. However, this in turn runs into turnback capacity limitations on the E in Manhattan, at the World Trade Center bumper tracks.

Potentially, NYCT could try to convert 36th Street into an express station, so that passengers could connect cross-platform. But such a dig would be costly and disruptive to operations. There were plans to do this at 59th Street on the 1/2/3 a few decades ago, for the transfer to the A/B/C/D, but nothing came of them.

Where new infrastructure is needed

The remaining reverse branches get increasingly more difficult. Already #7 requires new turnouts. The South Brooklyn trunk line has four tracks, but there’s not enough demand (or space in Manhattan) to fill them, so only the local tracks are used. There are occasional railfan calls for express service using the F, but it’s better to instead use the express tracks to segregate the G from the F. The G could be turned at Bergen Street on the local tracks, while the F could use the express tracks and then transition to the locals on new turnouts to be constructed at Carroll Street.

Also in the category of requiring new turnouts is #1: Rogers Avenue Junction is set up in a way that briefly forces the 2, 3, and 5 trains to share a short segment of track, limiting capacity. This can be resolved with new turnouts just east of the junction, pairing Nostrand Avenue Line with the local tracks and the West Side and the portion of the Eastern Parkway Line east of Nostrand with the express tracks and the Lexington Avenue Line. Trains on Eastern Parkway could either all go local, or keep the current mixture of local trains to New Lots (currently the 3) and express trains to Utica (currently the 4), skipping a total of two stations. This fix also reduces passengers’ access to one-seat rides, but at least there is a reasonable cross-platform transfer at Franklin Avenue, unlike on Queens Boulevard or at 145th Street and St. Nicholas.

And then there is #2, by far the most difficult fix. Demand on the White Plains Road branch in the Bronx is too strong to be a mere branch: the combined number of boardings at all stations is 166,000 per weekday, and besides, the line branches to Dyre Avenue near its outer end and thus needs the frequency of either a trunk or two branches to ensure adequate service to each other branch. This is why it gets both the 2 and 5 trains. There is unfortunately no infrastructure supporting a switch eliminating this track sharing: the 4 and 5 trains could both use this line, but then the 2 has no way of connecting to Jerome Avenue Line without new tunnels.

On the map, I propose the most obtrusive method of fixing this problem: cutting the 3 trains to a shuttle, with a new pocket track at 135th Street, letting passengers transfer to the 2, ideally cross-platform. With all through-trains running on the 2, there is no need (or space) for the 5 on White Plains Road, and instead the 5 should help boost the frequency on Jerome Avenue. In addition, some work is required at Woodlawn, which currently has bumper tracks, fine for a single branch but not for a non-branching trunk line (the bumper tracks on the L limit throughput to 26 tph no matter how good the electronics are).

Additional infrastructure suggested by deinterlining

Deinterlining is a service increase. Lines that today only get half or two-thirds service would get full trunk frequency: Second Avenue Subway would get the equivalent of the Q and N trains, the Astoria Line would get the entirety of 60th Street Tunnel’s capacity, Eighth Avenue would get more express trains, and 63rd Street Line and the South Brooklyn Line would get more than just the half-service of the F. With six track pairs on the lettered lines through Midtown and six north and east (Central Park West*2, Second Avenue, Astoria, Queens Boulevard*2), there is no room for natural branching to give more service to busy areas than to less busy ones.

One solution to this situation is targeted development on weak lines. Even with half service, South Brooklyn has underfull F trains, and Southern Brooklyn’s B, D, N, and Q trains aren’t much busier, making this entire area an attractive target for upzoning.

However, it’s more interesting to look at lines with extensions that suggest themselves. Second Avenue Subway has the obvious extension north to Harlem in phase 2, and a potential subsequent extension under 125th Street to Broadway, which is less obvious but popular among most area railfans (including one of my inside sources at NYCT). The Astoria Line has a natural extension to LaGuardia, ideally elevated over Ditmars to capture local ridership on Astoria as well as airport traffic; while the steel el structures in New York are soundboxes, it is possible to build quieter els using concrete (as on the 7 el over Queens Boulevard in Sunnyside) or a mixture of concrete columns and a steel structure (as on the Metro 2 and 6 els here in Paris).

The Nostrand Avenue Line provides an especially interesting example of a subway extension suggested by deinterlining. The terminal, Flatbush Avenue, was intended to be temporary, and as a result has limited turnback capacity. To prevent it from constraining the entire 2 route, which became the city’s most crowded even before Second Avenue Subway began decongesting the 4 and 5, it would be prudent to extend the line to Sheepshead Bay as the city intended when it planned the line in the 1910s.

In contrast, a subway extension under Utica, a stronger bus corridor than Nostrand with a strong outer anchor at Kings Plaza, loses value under deinterlining. It could only get a branch and thus have lower capacity than Nostrand. It would also definitely force branching on the express trains, whereas without such an extension they could run as a single unbranched line between Woodlawn and New Lots Avenue via Jerome Avenue, Lexington Avenue, and Eastern Parkway. A Utica subway should wait until there is political will to fund an entirely new crossing into Manhattan, presumably via Williamsburg to help decongest the L.

A second extension I have occasionally mooted, a subway under Northern, loses value even more. Such a subway would be a fourth trunk line in Queens and have to come at the expense of capacity on Queens Boulevard. It is only supportable if there is an entirely new tunnel to Midtown, passing under the mess that is the tracks in Long Island City.

A deinterlined New York City Subway

Fast Forward proposes moving block signaling on the most crowded subway segments, but typically only on trunks, not branches, and in some cases not even entire trunks. But in the long term, New York should transition to moving blocks and automation on all lines – at the very least the highly automated system used on the L, but ideally fully driverless operation, in recognition that wages are going up with economic growth but driver productivity isn’t. Simultaneously, deinterlined operations should allow tph counts in the mid 30s or even more (Metro 13 here runs 38 tph and Metro 14 runs 42).

Instead of the potpourri of lines offered today, there would be fewer, more intense lines. Nomenclature would presumably change to deal with the elimination of some services, clarifying the nature of the subway as a nine-line system in which five lines have four tracks and four lines have two. Each of these fourteen track pairs should be able to support a train every 90-105 seconds at the peak; not all lines have the demand for such frequency, and some have capacity-limiting bumper tracks that aren’t worth fixing (e.g. the 1 at Van Cortlandt Park), but many lines have the infrastructure and the demand for such capacity, including the express lines entering Midtown from Uptown or Queens.

Off-peak, too, service would improve. There is ample capacity outside rush hour, but turning the system into one of lines arriving every 4-5 minutes with strategic transfers rather than every 8-10 minutes would encourage people to take the trains more often. The trains would simultaneously be faster and more reliable, since incidents on one line would wreck service on other trains on the same line but leave the rest of the network unaffected.

With service improvements both during and outside rush hour, New York could expect to see substantial increases in ridership. Raising peak frequency from the current 24 tph to 36 tph on the busiest lines (today’s 2/3, 4/5, A/D, and E/F) is equivalent to building an entirely new four-track subway trunk line, and can be expected to produce similar benefits for passengers. The passups that have become all too familiar for riders on the 4, L, and other busy trains would become a thing of the past unless ridership rose 50% to match the increase in capacity.

Consumption Theory and Gentrification

I recently saw an article about location decisions by education in the Netherlands. The article discusses the impact of rail investment on different social classes, and claims that,

A recent study by Teulings et al. (2018) uses microdata to quantify the differences in the willingness to pay for particular locations between the high and low educated (omitting the medium education level) (Figure 2). It shows willingness to pay for the job availability (based on the locally available transport infrastructure to commute to these jobs) and urban amenities such as parks and historic scenery at the location. The highly educated (right panel) are very sensitive to the quality of a location.

The claim is that educated people prefer central cities, in this case Amsterdam, because of their consumption amenities. This is the consumption theory of gentrification, which holds that the process of gentrification is caused by a middle-class taste for urban amenities. However, this theory appears incorrect, on several levels. The references cited in the paper for location decisions do not really bear out consumption theory. Moreover, the history of gentrification strongly suggests that, if consumption amenities are at all involved, then they have been stable for at least a hundred years.

Instead of consumption theory, the best explanation is that location decisions are about jobs. Certain cities have higher production amenities, especially for the middle class, leading the middle class to preferentially move to them to obtain higher-income jobs. The choice of neighborhood is then driven by access to skilled jobs, usually in the CBD but sometimes also in new job clusters. If there’s gentrification, the cause is insufficient housing in closer-in areas, leading to spillover to adjacent neighborhoods.

The references

The internal reference cited for it in the paper, the work of Coen Teulings, Ioulia Ossokina, and Henri de Groot, breaks down willingness to pay higher rents in expensive cities (i.e. Amsterdam) based on job access and several consumption amenities. The paper’s headline numbers superficially bear out consumption theory: table 7 on page 23 says that job availability is only responsible for 38% of low-education people’s variance in willingness to live in expensive cities and 28% of high-education people’s variance; the rest comes from amenities. However, a closer reading suggests that this is not really about consumption amenities.

First, that 28% of middle-class location choice comes from job access does not mean 72% comes from amenities. Observed consumption amenities are only 18% (and only 14% for low-education workers); the rest is unobserved amenities (30%), which are a residual rather than any identified amenities, and covariances between jobs and amenities.

Moreover, the consumption amenities listed are proximity to restaurants, monuments, parks, and a university. Is a university really a consumption amenity for the middle class? This is unlikely. Graduates don’t really have the same consumption basket as students. Instead, what’s more likely is that universities provide skilled employment for a particular set of high-education workers (namely, academics and other researchers), who are willing to pay extra to be near work; academic job markets are so specialized that access to non-academic high-education work isn’t as important. Of course, universities also have extensive working-class employment, but a university janitor can get a similar job at a non-academic environment, and therefore has no reason to locate specifically near a university rather than another source of work, such as a hospital or office building.

Finally, there is a second reference in the article, reinforcing its claims about location decisions with American data. This is a paper by David Albouy, Gabriel Ehrlich, and Yingyi Liu. Albouy, Ehrlich, and Liu’s text does not endorse consumption theory – on the contrary, their discussion blames “policies and regulations that raise rents by creating artificial shortages in housing supply” (pp. 28-29). On the question of consumption theory, the results of the study are inconclusive. They do not look directly at amenities that critics of gentrification typically implicate in causing the middle class to displace the poor; the amenities they consider include mild climate, clean air, and a sea view.

The history of gentrification

The word “gentrification” was coined in 1964 to describe the process in Islington. However, Stephen Smith has argued from looking at historical rents that the process goes much further back. He finds evidence of gentrification in Greenwich Village in the 1910s and 20s. Already then, the middle class was beginning to move into the Village, previously a working-class district. Jane Jacobs moved in in 1935. She was income-poor, as were many other people in the Depression, but on any marker of class, she was solidly comfortable: her father was a doctor, she herself was a high school graduate and had some college education at a time when most Americans had never gone to high school, and her job was in journalism, at the time a middle-class career path.

In the 1950s and 60s, this process continued in full swing, in the Village and other inner neighborhoods of New York, such as the Upper West Side, which unlike the Upper East Side was originally rowdy (West Side Story is set there). Developers were building taller buildings, to Jacobs’ consternation, to house the growing middle-class demand.

I focus on early gentrification in New York and not London, because in this era, the American middle class was fleeing cities. In the 1950s New York was poorer than its suburbs. The wealthiest strata of the city had decamped to Westchester and Fairfield Counties starting in the 1910s and 20s (in 1930 Westchester had 520,000 people, more than half of today’s level, and more than Long Island). Then in the 1950s and 60s this process spread to the entire white middle class, causing a population surge on Long Island, in New Jersey, and in the parts of Westchester and Fairfield that the rich hadn’t already settled in. Moreover, companies were moving out of city centers, often to be closer to the CEO’s home, including General Electric (which moved to the town of Fairfield in 1974) and IBM (which moved to Armonk in 1964). Middle-class taste at the time was firmly suburban.

A better explanation for the early history of gentrification in New York concerns the subway. Before the subway opened, the working class had to live right next to the Lower Manhattan CBD and commute on foot. The els did provide some options for living farther uptown, but they were slow and noisy (they were only electrified around the time the subway opened) and until the early 20th century the working class could not afford the 5-cent fare. This led to extreme levels of overcrowding just outside the CBD, most infamously on the Lower East Side. In 1900, most of Manhattan was open to the middle class but only the Lower East and West Sides were open to the working class. By 1920, the fast subway and the 5-cent fare (held down despite post-WW1 inflation) made all of Manhattan open to everyone, making it easier for the middle class to outbid the poor for housing in the Village.

Production theory

The paper cited at the beginning of this post does not profess consumption theory; it claims that both production and consumption amenities explain gentrification. However, the actual work within the paper leans heavily toward production. It looks at the effect of opening a new rail line from the suburbs to Amsterdam, and finds that this leads to middle-class displacement of lower-education residents, who have less use for the train service. This is also consistent with what working-class residents of some Parisian banlieues think: a newspaper article I can no longer find cites people within Seine-Saint-Denis complaining that all Grand Paris Express will do is raise their rents.

In addition to being more consistent with Dutch and American evidence and American history, production theory benefits from not relying on special local explanations for a global trend. A process that began at similar development levels in the US and Western Europe is unlikely to be about American race relations. Even Tokyo is seeing gentrification in the sense that industrial waterfront areas are redeveloped, if not in the sense of mass displacement seen in New York, London, and other cities with stricter zoning.

There is no burning middle-class desire to live near poor people – quite the opposite, in fact. When the middle class does begin gentrifying a neighborhood, it’s because it offers convenient access to jobs. The same is true on the level of an entire city: San Francisco did not magically become a nicer place to live in when the current tech boom began – if anything, rising rents have led to a homelessness problem, which makes professional workers uncomfortable. A city that wishes to forestall gentrification will make it easy to build housing in the areas with the best job access, in order to encourage people to have short commutes rather than seeking increasingly marginal neighborhoods to move to.

Why is Second Avenue Subway Phase 2 So Expensive?

I am only loosely following the news about the second phase of Second Avenue Subway. The project, running from 96th Street to 125th, with a short segment under 125th to Lexington, passing under the 4, 5, and 6 trains, is supposed to be cheap. In the 1970s, work began on Second Avenue Subway before the city went bankrupt, and there are extant tunnel segments built cut-and-cover in East Harlem between the station sites. The stations need to be dug, but the plan dating back to 2003 was to build them cut-and-cover as well, with local disruption for only a few blocks around 106th, 116th, and 125th Streets. Only one part would be difficult: going deep under 125th, under the preexisting subway. And yet, costs are very high, and the design seems to be taking a wrong turn.

In the early 2000s, the cost projections were $3.7 billion for phase 1 (actual cost: $5 billion, but much of the difference is inflation), and $3.3 billion for phase 2 (projected cost: at least $6 billion). Since then, there have been changes. For about a year I heard rumors that the preliminary engineering had been done wrong, and it was impossible to use the preexisting tunnel segments. Then I heard that no, it’s actually possible to use the existing tunnels. But a few days ago I heard that even though it’s possible, the MTA is now planning to demolish the existing tunnels and build the entire project deep underground using tunnel-boring machines.

With the information generally given out at community meetings, it’s hard to know what’s exactly going on. However, the fact that the MTA is talking about this suggests extreme disinterest in cost control. Cut-and-cover construction is cheaper than TBMs, per a 1994 paper looking at French urban rail costs since the 1970s. The tradeoff is that it forces rail lines to go underneath streets, which is disruptive to pedestrians and merchants, or demolish private property. Fortunately, Second Avenue is a wide, straight throughfare, and requires no such demolitions, while the disruption would be localized to areas that are scheduled to get subway stops as part of the project. Metro extensions here and in a number of other European cities are constructing stations cut-and-cover and the tunnels between them with TBMs; Metro Line 12’s online documents state that station construction involves just 18 months of digging.

It’s possible that the need to turn to 125th Street is messing up the plan to do everything cut-and-cover. While the turn itself can be done with minimal demolitions (the inside of the curve has a few small buildings, and there’s also an alignment slightly farther east that goes under vacant land while maintaining a 90-meter curve radius), going underneath the Lexington Avenue Line requires diving deep, and then there is no advantage to cut-and-cover. Building cut-and-cover under existing lines is difficult, and in that case, TBMs are warranted.

If the problem is 125th Street, then I would propose extending phase 2 and then breaking it apart into two subphases. Phase 2.0 would be cut-and-cover and open stations at 106th, 116th, and possibly 125th and 2nd temporarily. Phase 2.5 would involve driving TBMs under 125th Street all the way to Broadway; this could be done with a large-diameter TBM, with the platforms contained within the bore and vertical access dug so as to avoid the intersecting north-south subways. 125th Street has 30,000 crosstown bus boardings according to the MTA, which would make it the busiest bus corridor in the city per km: 10,000 per km, compared with 8,000 on the busiest single route, the M86. It is a priority for subway expansion, and if it’s for some reason not possible to easily build from 96th and 2nd to 125th and Lex in one go then the entire project should be extended to 125th and Broadway, at somewhat higher cost and far higher benefits.

The reason phase 1 was so expensive is that the stations were mined from small digs, rather than built cut-and-cover as is more usual. The idea was to limit street disruption; instead there was street disruption lasting 5 years rather than 1.5, just at small bore sites at 72nd and 86th rather than throughout the station boxes’ footprints. The TBM drive and systems cost together $260 million per kilometer, compared with $125 million on Paris’s Metro Line 1 extension, but the stations cost $750 million each, compared with $110 million.

It’s crucial that the MTA not repeat this mistake in phase 2, and it’s crucial that area transit activists hold the MTA’s feet to the fire and demand sharp cost control. Even taking the existing premiums as a given, cut-and-cover stations should not cost more than $200 million each, which means phase 2 as planned should cost $600 million for stations, about $330 million for systems, and another $350 million for overheads. At $1.3 billion this still represents high cost per kilometer, about $500 million, but it’s based on actual New York cost items, which means it’s plausible today. There is no excuse for $6 billion.